SPO Cube data load inconsistent in SAP BW 7.3

We are using SAP BW 7.3 SP level 10. we noticed some issues with a SPO cube which is fed from a standard DSO via process chain. It's on delta run DTP. however, every now and then , SPO cube ends up to be holding incorrect data compare to the underneath DSO. After deleting data from SPO cube and reload, SPO cube works fine for a while and falls over again.

So we are not sure what would be the permanent solution. Did anyone come across such issue. Any advice or suggestion would be appreciated.